Actually, on reflection, the one who was 9 years younger was Mr. Big Lots, who I didn't meet online but who picked me up when I was shopping. So I guess my online dates ranged from 2 years older (my first boyfriend) to the rest being between 4-6 years younger. I'm leaving out the couple of inappropriately younger guys who initiated contact and who I briefly dated - they were definitely below my 10 year age difference limit.
I will say almost all the men list their desired age range as either their age and younger, or no more than 2 years older and younger. So some of you guys might have better response rates if you at least look at women up to 5 years older.